1. Field of the Invention
This invention relates to photographic cameras, and more particularly to an electromagnetically operating release control device for such camera which enables a film winding-up operation not to interfere with a releasing operation subsequent thereto.
2. Description of the Prior Art
Most of the release mechanisms for photographic cameras are designed to be made actuable after a film winding up operation has been completed. This design feature is also employed in a camera provided with an electromagnetically operating release mechanism so that a release therefor operation is initiated at the simultaneous occurrence of two distinctive signals from respective means cooperating with a shutter release button and a film winding lever as these signals are applied to a control means for a single electromagnet in the release mechanism. This control means takes usually an AND gate circuit form so that, upon simultaneous reception of the above identified two signals, an output signal is produced which is utilized in controlling an actuation of the electromagnet.
The release mechanism of such construction must be provided with control means for coordination with a resetting mechanism having a manually operating member which is common to a film advancing mechanism, that is, the film winding lever, or otherwise a film winding up operation would often interfere with a camera releasing operation subsequent thereto when the film winding lever is operated while the shutter release button remains depressed either accidentally or intentionally. This is particularly true when the camera is driven by a motor drive unit. In other words, as the film winding up lever must be over-cocked past the end of a film winding stroke to effect the returning movement of the resetting mechanism to its idle position, a release of an automatic diaphragm control mechanism, a mirror drive mechanism, a shutter control mechanism and the like is caused to start at the time when movement of the film winding lever has reached the above identified stroke end, provided that this time occurs during the depression of the shutter release button. It is known to provide such coordination control means in the form of a delay circuit having a time constant necessary for the film winding lever to move from the stroke end to an over-cocked position where the film advancing mechanism assumes its starting position and arranged between the AND gate circuit and the electromagnet. This conventional arrangement of the delay circuit has a disadvantage such that even when the completion of the film winding up operation is followed by the depression of the shutter release button, duration of an unnecessary delay time interval occurs from the depression of the shutter release button to the actuation of the shutter mechanism.
Accordingly, the present invention has for its general object to eliminate the above mentioned disadvantage of the conventional camera.
According to an aspect of the invention, operation signal forming means produce an operation signal in response to operation of a release button, winding signal forming means produce a winding signal in response to operation of a film winding mechanism, delay means respond to the winding signal to produce a delay signal or predetermined time after the winding signal, gate means produce a release signal upon receiving the operation and delay signals, and power supply control means energize electromagnetic release means in response to the release signal.
By virtue of these features initiation of the electromagnetic release means is deferred by a time interval slightly longer than necessary for the film winding lever to move from the film advancing stroke end to the over-cocked position at normal speed. Thus, the electromagnetic release is initiated by the shutter release button when the film winding operation is followed by depression of the button.
According to another aspect of the invention, the delay means include a time constant circuit composed of a resistor and a capacitor. According to another aspect of the invention the gate means is in the form of an AND circuit.
According to another aspect of the invention, first input means produce a winding completion signal and second input means produce a release actuation signal. A flip-flop produces a high signal from a first output terminal when a signal from the first input means is applied to a first input terminal and produces a high signal from a second output terminal when a signal from the second input means is applied to a second input terminal. First gate means produce a signal in response to simultaneous receipt of the winding completion signal and the release actuating signal. Second gate means produce a signal when both a winding completion signal and the high signal from the first output terminal are applied thereto. Third gate means produce a signal in response to simultaneous receipt of signals from the first input means and the second output terminal. Electromagnetic release means actuate the operating mechanism of the camera from either the second gate means and the third gate means, and delay means between the electromagnetic release means and the second release means apply the signal from the second gate means to the electromagnetic release means only after a predetermined time has passed.
According to another aspect of the invention, the first and second input means have respective pulse generating means connected to the respective input terminals of the flip-flop circuit.
According to another aspect of the invention, fourth gate means apply a signal to the electromagnetic release means when one of the signals from the delay means and the third gate means is applied thereto.
According to another aspect of the invention, second delay means apply a signal to the second gate means and the third gate means after the output of the first gate means is delayed by a predetermined time.
According to still another aspect of the invention, a mode selector switch between the first delay means and the fourth gate means has one position for continuous sequential operation.